Day/night temperature affects growth and photosynthesis of cultivated Salvia taxa

Abstract

Eight taxa of Salvia L., representing broad geographic origin and diversity within the genus, were grown under long day conditions for 36 d at 15-h days of 20, 25, 30, 35, or 40 °C and 9-h nights of 15 or 25 °C. Taxa of European origin displayed broader tolerance to high day temperatures (DTs) with the lowest relative reduction in growth and net photosynthesis (Pn) occurring at DTs 30 °C or greater compared with those native to North and South America. Salvia splendens Sell. ex Roem. & Schult. (scarlet sage) was particularly intolerant of high temperatures with all plants dying at days of 40 °C. All plants of S. nemorosa L.'Ostfriesland' ('Ostfriesland' wood sage), S. pratensis L. (meadow sage), and S. x sylvestris L. 'Mainacht' ('May Night' salvia) survived at days of 40 °C with no visual signs of injury, whereas all other taxa except S. splendens exhibited stunted, contorted growth with foliar chlorosis and necrosis at 40 °C. Day temperature exerted the primary effect on top growth, root growth, and Pn of all taxa. Night temperature effects were significant for some taxa but were of less importance than day temperature.